Motor port construction



March 31, 1953 J. A. LAUCK ETAL 2,633,104

MOTOR PORT CONSTRUCTION Filed July 15, 1949 2 SHEETSSHEET 1 March 1953J. A.'LAUCK ETAL 2,633,104

MOTOR PORT CONSTRUCTION I Filed July 15, 1949 2 SP-IEET S-SHEET 2fnveriors: \J-OIZLTL Q. .L auck and 2| so that the total area of areas22a exceeds that of 22b by a slight margin in accordance withestablished pressure loading practice. A pair of radially spaced,annular grooves 220 formed in the left end surface of block 2| anddisposed coaxially of shaft |4 define the inner and outer periphery ofareas 22?) and communicate with the sump of the transmission throughradially outwardly extending grooves 2201, as shown in Fig. 1.

Cylinder block 2| is supported on and splined to shaft l4, and a piston23 is slidably journalled in each of the cylinders 20. Each piston 23has associated therewith a piston rod 24 whereby connection is madebetween the piston and a swash or wobble plate assembly designatedgenerally at 25. To provide a suitable connection, at each end of eachconnecting rod 24 a ball 26 is mounted, the ball at the left end beingreceived in a suitable spherical recess 21 formed in the associatedpiston, while the ball at the right end of the connecting rod isreceived in a socket cup 30 mounted in the swash plate 25. Thesespherical terminations permit angular displacement of the connectingrods 24 with respect to the axis of reciprocation of the pistons 23 asthe position or inclination of the swash plate 25 is changed.

More specifically, the swash plate assembly 25 comprises an inner,annular, dish-shaped socket housing 32 which is pivotably supported ona-constant velocity universal joint 3| and an outer, generally annular,supporting carrier or bed 33, the angular position of which may bevaried with respect to shaft l4 about an axis lying transverse to theaxis of shaft M. A constant velocity universal joint is essential inorder that uniformity of transmission of motion be provided. In aconstant velocity universal joint of the type illustrated, the point ofcontact, or of motion transfer, is always at equal radial distances fromthe axes of the two elements, that is the point of contact always liesin the plane bisecting the angle between the connected elements.Constant velocity universal joint 3| is of generally conventional designand is splined on shaft l4 adjacent the right end of a motor block 2|.An annular bearing assembly 34 is interposed between the outer member 33of the swash plate and the socket housing 32 so that the socket housing32 may rotate with respect to the outer member 33 in a plane determinedby the angular position of the outer member. The socket cups 30 aredisposed in annular array about the left face of housing 32, beingreceived in suitable apertures 35 formed in the housing and secured tothe housing as by welding or swaging.

Outer member or carrier 33 is supported on a pair of oppositelydisposed, radially extending stub shafts 36 and 31, as shown in Fig. 1,journalled in suitable, axially aligned trunnion bearings indicatedgenerally at 38, which bearings are mounted between the housing sectionsI and I2. Stub shaft 31 is keyed to the angularly adjustable carrier 33of the swash plate 25 by a pin 39 which extends transversely through theshaft and into the carrier. Thus, by rotating shaft 31, the angularadjustment or inclination of the swash plate assembly 25 may becontrolled.

It will be evident that with this arrangement, torque is applied to theshaft M from the socket ring which is, in effect, splined to the shaft,through supporting universal joint 3|. The swash plate assembly is thuspivotable about the axis of stub shafts 36 and 31, and the sockethousing 32, while rotatable relatively to the supporting carrier 33 asthe hydraulic motor block and shaft M are rotated, is not rotatable withrespect to shaft l4. By rotating stub shaft 31 and thereby pivotingcarrier 33, the relative inclination of swash plate assembly 25 may bechanged, and the effective displacement of the hydraulic motor may thusbe varied from a minimum when the plate is at right angles to shaft M toa maximum as the inclination toward the shaft I4 is reduced in eitherdirection.

In order to control the application of pressure to the hydraulic motor,the pressure control assembly housing It) mounted at the left end ofmotor housing section H, has formed therein a pressure chamber 40 and asuction chamber 4|. Both chambers are suitably connected through ducts,not shown, to a pressure generator, such as a gear pump, the chamber 4|]being connected to the outlet side of the pump and the chamber 4| beingconnected to the inlet side thereof. A suitable arrangement is shown anddescribed in the co-pending application of Minshall et al., Serial No.104,924 filed July 15, 1949.

The right end wall of housing section I0 has a wide recess 42 ofgenerally cylindrical configuration formed therein to receive themanifold porting plate 43, and plate 43 is rigidly secured to housing l0by bolts 44. It will be noted that a slot 45 is formed in the upper edgeof the porting plate, as viewed in Fig. 1, and a locating pin 46 mountedin the right end wall of the housing section l0 extends into the slot45. This pin and the cooperating slot facilitate proper location of themanifold porting plate during assembly of the transmission. Manifoldporting plate 43 has formed therein on the left side thereof, as viewedin Fig. 1, two sets of cylindrical porting recesses 41 and 48,respectively, which communicate at their right ends with two generallyarcuate kidney ports 50 and 5|, respectively, formed by recessing theright surface of plate 43. Kidney port 50 constitutes the pressure portof this transmission in normal operation and registers at the left sidethereof, as viewed in Fig. 1, through porting recesses 41 with the rightend of a passage 52, the left end of passage 52 connecting with pressurechamber 4|). Similarly, the left side of kidney port 5| registersthrough porting recesses 48 with the right end of a passage 53 formed inhousing section II), and the left grlid of passage 53 connects withsuction chamber Ports 22 formed at the left ends of cylinders 20 of thehydraulic motor are arranged so that as the motor block 2| rotates onthe shaft M, the ports 22- will sequentially register with the kidneyports 50 and 5| in the manifold porting plate, thus alternately applyingpressure and then suction to the cylinders. When the motor is operatingthe pressure in the cylinders, by virtue of the selection of pressureareas 22a and 22b, is sufficient to provide a tight seal between theleft end surfaces of the motor block and the right end surfaces of themanifold plate 43, both of which surfaces are ground flat and smooth. Inorder to maintain these surfaces in suitable contact when no load istransmitted, however, a helically coiled spring 54 is disposed on asleeve portion 55 of the universal joint 3|, the sleeve 55 being mountedon and keyed to shaft i4 and extending into a deep cylindrical recess 56formed at the center of the motor cylinder block. The left end of spring54 bears against the inner end wall of recess 56, while the rightportion of spring 52 bears against a re- 5 taining ring 51, which isheld in position on sleeve 55 by-a shoulder 58 formed about theperiphery of the sleeve '55 adjacent its right end.

Heretofore, it has been the general practice to form the arcuate kidneyports 50 and 51 in a coring operation whereby the ends of the ports wereslightly tapered but on the whole of generally semicylindricalconfiguration. In accordance with the present invention, however, it hasbeen discovered that the configuration of the kidney ports, andparticularly the terminations thereof, must be critically designed inorder to obtain smooth and eific'ient operation of the transmission andto avoid the objectionably noisy operatien, heretofore often consideredan inherent characteristic of this type of transmission.

In Fig. 3, a curve 60 is presented illustrating the travel of ahydraulic motor piston from top dead center to bottom dead centerposition, Fig. 3 thus illustrating half of a piston cycle, both halvesof the cycle being identical. From this graph itwill be noted that theinitial movement of the piston, starting from the rest position, whichcoincides with vertical line I), is one of increasing "acceleration. Bythe time the piston has reached a position designated at 61 andapproximately coinciding with vertical line 4, a substantially constant"velocity is reached. The velocity remains constant then during themajor portion of piston travel and until a position designated at 62 isreached, coinciding approximately with vertical line 3, after which thepiston begins toslow down preparatory to stopping and reversingdirection of movement. .At position 63, representing bottom deadreenter, the piston is again at rest. This curve is typical of normaloperation and may be regarded as characteristic of piston travel in thistype of motor.

Referring now to Fig. 4, wherein a curve 64 is presented representingthe pressure within .a

cylinder plotted against piston travel during the power stroke using aconventional cor-d porting arrangement, as described, it will be evidentthat as the cylinder port 22 begins to register with the end ofaconventional kidney port theresis an initial momentary, gradualapplication of pressure,but when the port "22 has moved only a veryshort distance, full registry is obtained and maximum pressure isabruptly applied.

This maximum pressure is thus applied prior to the time that pistontravel has reached or can reach maximum velocity, that is, the .zone ofconstant velocity, and consequently the piston is undesirably loaded.After the piston has delivered its useful work during the power strokeportion of its cycle of operation and has begun to slow down, that is tosay is operating on the portion of curve '60 lying between points 62 and63 "in'Fig. 3,1naximum pressure is still applied since itis desirablethat the piston deliver full power to the end of its power stroke.Actually, there may be an actual sharp chamber pressureincreaseimmediately preceding the pressure exhaust phase due tothe'failure 'ofprior portingarrangements to provide a graduatedreduction in inlet flow proportioned to the deceleration of the pistonas it reaches the end of its power stroke. Thereafter,

upon registration of the motor port with the exhaust passage intheporting plate there is an equally abrupt release of pressureirom thepiston chamber. From the foregoing it will be evident that considerablepressure wasted since during a substantial portion of piston travel ineach cycle, the piston actually reacts against application of pressurerather than responds thereto. In

6 addition to this loss of power with resulting reduction in thepossible .efliciency of the transmission, the abrupt admission andrelease of pressure causes the transmission to be undesirably noisy.

In accordance with the present invention, the terminations of each ofthe kidney ports 501and ii are tapered in such a manner that the rate offlow or the fiu'identering the cylinders is made to be in directproportion to the pistonveloc'ity at any instant from top dead centerposition to bottom dead center position. Stated otherwise, thekidneyports are so constructed and their ends are tapered so that the volumeof fluid flow into the piston chamber at any instant is proportioned orselected to provide a piston energizing pressure commensurate with thecapacity or the piston to reactor move at that instant. Thus, instead ofabruptly applying maximum fluid pressure to the "piston during theinitial phase of movement when the piston is moving relatively slowlyand can only move relatively slowly, the pressure in accordance withthis invention is also applied relatively slowly and at a rate selectedto take maximum advantage of the travel charac teristic of this type ofpiston without wasting fluid pressure. This not only results in -materially increased operating eiiiciency but a tion and later withdrawalof pressure is provided paralleling insofar as possible the power strokeand exhaust stroke phases of piston travel, as shown in Fig. 3.

To some extent, the degree or taper of the fish tails 59a and em may becalculated in advance,

since the degree of taper is directly related to the portion of thecurve Gillying between top dead center position and position 6i and alsothe portion of the curve lying betweenpoint E2 and bottom dead centerposition designated 63 in Fig. 3. For any particular transmission,however, it has been found that the final design must be worked outexperimentally. Curve '65 of Fig. 4 represents a desirable pressurevalue characteristic applied to the piston, that is, the displacementchamber within the motorcylinder plotted against piston travel from thestart position, .or bottom dead center, of the power stroke through theend of the power stroke and to approximately the beginning of theconstant velocity portion of the exhaust stroke. From this curve it willbe evident that pressure is applied at a graduallyincreasing ratestarting from bottom dead center position and over substantially theentire accelerating portion of travel of the piston. Thus, for example,considering the direction as being clockwise as to Fig. 2, a motor portregisters at its right edge with the upper the piston, thus tending toprovide a constant value maximum chamber pressure during this period ofmaximum piston velocity. Thereafter, as the motor port begins toregister with the start of the tapered termination at the lower end ofkidney port i), the rate of flow of fluid into the piston chamber isgradually reduced paralleling the reduction in piston velocity butmaintaining a constant chamber pressure value. If the rate of flow offluid were not reduced concurrently with the reduction in velocity ofthe piston, and at a rate paralleling the reduction in piston .velocity,there would be an undesirable rise in chamber pressure during the lastpart of the pressure stroke.

After the end of the piston power stroke, the associated motor port foran instant is in registry neither with the inlet kidney port nor theoutlet kidney port and maximum pressure is maintained in the pistonchamber. However, continued rotation of the motor block in a clockwisedirection then brings the leading edge of the motor port in registrywith the lower, tapered termination Sl-a of the exhaust port 5|. The

. operation here is the reverse of that during the .power stroke,pressure in the piston chamber being released at a gradually increasingrate during the accelerating phase of piston travel on the exhauststroke up to a maximum rate coinciding with the maximum velocity phaseof the exhaust stroke. The rate of exhaust is thereafter reduced toparallel the piston velocity characteristic during the deceleratingphase of the piston exhaust stroke as the motor port registers with theupper tapered termination 5l-a of the exhaust port. It will be apparentthat the present arrangement lends itself equally well to rotation ofthe motor block in either direction.

When the transmission is in a neutral position, that is to say, thevehicle with which it may be associated is not moving, if a cylinderport 22 is located at the dead center position, that is located exactlybetween manifold plate porting openings, considerable difiiculty may beencountered in attempting to shift the inclination of the swash plateassembly. This is due to the seal provided between the manifold portingplate and left end of the cylinder block whereby fluid ;is substantiallyprevented from either entering or leaving a cylinder when a cylinderport does not register at least in part with either an inlet or outletmanifold port. In accordance with this invention, in order to permitshifting of the swash plate so that the torque multiplication ratio ofthe transmission may be changed, means are provided for admitting fluidto or exhausting fluid from a cylinder even though the cylinder port isnot in registry with a manifold port.

Referring to Fig. 1, it will be noted that a small aperture 66 is formedthrough the left end wall of cylinder block 2| radially outside of port22, the aperture 66 extending at a slight downward angle, as viewed inthis figure, from area 2211 to below groove 220. A short, radial slot 61is formed in the adjacent surface of manifold plate 43 and is adapted toregister at its radially inner end with the left end of aperture 66 whenthe associated port 22 is located between the two manifold plate ports56 and 5|. The other end of slot 61 communicates with the sump portionof the transmission. Thus, when an aperture 66 and slot 61 are inregistry, oil may be readily exhausted from or taken into the associatedcylinder, thereby facilitating shifting of the swash plate.

Where herein the various parts of this invenright or a left or an upperor lower position, it will be understood that this is done solely forthe purpose of facilitating description and that such references relateonly to the relative positions of the parts as shown in the accompanyingdrawings.

While but one embodiment of this invention has been shown and described,it will be understood that many changes and modifications may be madetherein without departing from the spirit or scope of the invention.

What is claimed is:

1. In a hydraulic displacement device adapted to operate as either ahydraulic pump or motor, a piston associated with said device, and amanifold porting plate for controlling application of pressure to andrelease of pressure from said piston, said manifold porting plate havingan exhaust port and a pressure port formed therein and said ports havinguniformly tapered terminations, the cross sectional area of said taperedterminations at the point of junction with said port being equal to thecross sectional area of the port end portion, the remaining crosssectional area of said tapered terminations varying according to thecharacteristic rate of change of volumetric size of said power pistonchamber accomplished by movement of said piston whereby the pressure ofthe fluid on said piston at any instant is in substantially directproportion to the piston velocity at that instant.

2. In a hydraulic transmission including a hydraulic motor of the typehaving reciprocable pistons journalled in cylinders formed in a cylinderblock, a shaft supporting said motor cylinder block and rotatabletherewith, each of said cylinders having a port formed therein, amanifold plate for controlling application of pressure to said cylindersand having ports formed therein, said cylinder ports being adapted toregister with said manifold plate ports, means for holding said manifoldplate stationary with respect to said rotatable cylinder block, and eachof said manifold plate ports having uniformly tapered terminations ateither end thereof, the cross sectional area of each of said taperedterminations at the point of junction with said port being equal to thecross sectional area of the port end portion, the cross sectional areaof the remaining portion of each of said tapered terminations varyingaccording to the characteristic rate of change of volumetric size ofsaid power piston chamber accomplished by movement of said piston sothat the rate of flow of the fluid entering and leaving the cylindersthrough the ports at any instant is in substantially direct proportionto the piston velocity at that instant.

3. A hydraulic displacement device comprising means defining a pistonchamber, a reciprocable piston in said chamber, said chamber having aport formed therein for admitting fluid to and releasing fluid from saidchamber, a manifold plate associated with said piston chamber definingmeans, and having a pressure port and an exhaust port formed therein,said manifold plate ports and said chamber port being adapted to moveinto registry, and each of said manifold plate ports having uniformlytapered terminations at either end thereof, the cross sectional area ofeach of said tapered terminations at the point of junction with saidport being equal to the cross sectional area of the port end portion,the remaining cross sectional area of each of said tapered terminationsvarying according to the characteristic rate of change of volumetricsize of said power piston chamber accomplished by movement of saidpiston whereby the rate of flow of the fiuid passing through saidchamber port at any instant is proportioned to the velocity of thepiston at that instant.

4. A hydraulic motor including a cylinder block having a piston chamberformed therein, a piston reciprocable in said chamber, means defining aport associated with said chamber for controlling the admission of fiuidpressure to and the release of fiuid pressure from said chamber, saidport having an elongated configuration with tapered terminations ateither end and an intermediate portion joining said termination ofuniform width and being arranged so that the effective size of said portat any instant is varied in accordance with the velocity at that instantof said piston, said effective size of said tapered terminations beingaccomplished by providing said tapered terminations with a crosssectional area equal to the cross sectional area of the port end portionand varying the cross sectional area of the remainder of said taperedterminations according to the characteristic rate of change ofvolumetric size of said power piston chamber accomplished by movement ofsaid piston, one of said tapered terminations being arranged to providea uniformly increasing application of hydraulic pressure to said pistonchamber during the accelerating phase of the power stroke of saidpiston, the intermediate portion of said port providing a substantiallyconstant pressure in said piston chamber during the substantiallyconstant velocity phase of the power stroke, and the other of saidterminations providing a substantially constant chamber pressure duringthe decelerating phase of the power stroke.

5. A hydraulic motor including a cylinder block having a plurality ofpiston chambers formed therein and disposed in annular array, a shaftsupporting said cylinder block, a piston reciprocable in each of saidchambers, each of said chambers having a port formed therein, a manifoldplate having an exhaust port formed therein and a pressure port formedtherein, said piston chamber ports being adapted to registersuccessively with said pressure and said exhaust ports, each of saidmanifold plate ports having uniformly tapered terminations at either endthereof joined by an intermediate portion of uniform width, each of saidtapered terminations having a cross sectional area equal to the crosssectional area of the port end portion, the cross sectional area of theremainder of each of said tapered terminations varying according to thecharacteristic rate of change of volumetric size of said power pistonchamber accomplished by movement of said piston, whereby each of saidpiston chamber ports in progressively registering with said pressureport first permits application of a uniformly increasing hydraulicpressure to the associated piston during the accelerating phase of thepower stroke of the piston, then registering with the uniform diameterportion of the pressure port in the manifold plate permits applicationof a uniform rate of pressure fiow to said piston, and finallyregistering with the tapered termination of the pressure port maintainsa substantially uniform pressure in said piston chamber during thedecelerating phase of the power stroke, and whereby said piston chamberport thereafter is progressively placed in communication with onetapered termination of the exhaust port so that during the accleratingphase of the exhaust stroke a uniformly increasing release of pressurefrom the piston chamber is permitted, then is progressively placed incommunication with the uniform diameter portion of the exhaust port sothat during the constant velocity phase of the exhaust stroke a constantrate of pressure release flow is permitted and finally is progressivelyplaced in communication with the other tapered termination of theexhaust port so that during the decelerating phase of the exhaust strokea uniformly decreasing release of pressure is permitted.

JOHN A. LAUCK. FRED C. HABERLAND.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 924,787 Janney June 15, 19091,081,810 Carey Dec. 16, 1913 1,867,308 Durner July 12, 1932 2,297,518Wegerdt Sept. 29, 1942 FOREIGN PATENTS Number Country Date 442,450 GreatBritain Feb. 10, 1936

